A single data point can be be used to represent millions of square kilometers. (theinconvenientskeptic.com)
The gray line shows the 1981 - 2010 average ice cover in millions of square kilometers. (treehugger.com)
Another challenge to food production and land and water conservation is the rising interest in vegetable - based biofuels, which requires the use of hundreds of millions of square kilometers of farmland and cleared rainforests. (treehugger.com)